Pumps and Fans are energy consuming equipment that can be found in almost all Industries. Therefore, it is important to check if they are running efficiently. This presentation give an overview about energy saving opportunities in pump and fan equipment. It was prepared in the context of energy auditor training in Nepal in the context of GIZ/NEEP programme. For further information go to EEC webpage: http://eec-fncci.org/
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Improving Energy Efficiency of Pumps and Fans
1. Energy Efficiency :Energy Efficiency :
AS RUN PERFORMANCE ASSESSMENTAS RUN PERFORMANCE ASSESSMENT
OF PUMPS AND FANSOF PUMPS AND FANS
D PAWAN KUMARD PAWAN KUMAR
2. AS RUN ENERGY PERFORMANCE ASSESSMENT OFAS RUN ENERGY PERFORMANCE ASSESSMENT OF
PUMPSPUMPS ::
Purpose of the As runPurpose of the As run
Performance Tests:Performance Tests:
• Determination of the pump efficiencyDetermination of the pump efficiency
during the operating conditionsduring the operating conditions
• Determination of system resistanceDetermination of system resistance
and the operating duty point of theand the operating duty point of the
pumps and compare the same withpumps and compare the same with
design.design.
3. Performance TermsPerformance Terms ::
Pump Capacity, Q = Volume of liquid delivered by pump per unit time,m3
/hr or m3
/sec
Q is proportional to N, where N- rotational speed of the pump
Total developed head, H= The sum of suction and discharge pressures
The pump head represents the net work done on unit weights of a liquid in passing from
inlet of the pump to the discharge of the pump.
There are three heads in common use in pumps namely
1.0. Static head
2.0. Velocity head
3.0. Friction head.
The frictional head in a system of pipes, valves and fittings varies as a function (roughly
as the square) of the capacity flow through the system.
System resistance: The sum of frictional head in resistance & total static head.
.
4. Pump Efficiency:Pump Efficiency:
Where,
Hydraulic power, Ph
(kW) = Q x (hd
- hs
) x ρ x g / 1000
Q = Volume flow rate (m3
/s), ρ = density of the fluid (kg/m3
), g
= acceleration due to gravity (m/s2
), (hd
- hs
) = Total head in metres
100
,
x
shaftpumpthetoinputPower
PpowerHydraulic
EfficiencyPump h
=
5. As run Trials for Determination of PumpAs run Trials for Determination of Pump
EfficiencyEfficiency
To determine the pump efficiency, three key parameters
are required:
Flow, Head and Power.
Of these, flow measurement is the most crucial parameter
as normally accurate online flow meters are hardly
available, in majority of pumping systems.
The following methods can be adopted to assess the flow
depending on the availability and site conditions.
6. Different Methods forDifferent Methods for
Flow MeasurementFlow Measurement , Q:, Q:
• Tracer method BS5857Tracer method BS5857
• Ultrasonic flow measurementUltrasonic flow measurement
• Tank filling methodTank filling method
• Installation of an on-line flow meterInstallation of an on-line flow meter
7. 1-Tracer Method1-Tracer Method ::
The Tracer method is particularly suitable for cooling water flow measurement because
of their sensitivity and accuracy.
This method is based on injecting a tracer into the cooling water for a few minutes at an
accurately measured constant rate. A series of samples is extracted from the system at a point
where the tracer has become completely mixed with the cooling water. The mass flow rate is
calculated from:
qcw = q1 x C1/C2
where qcw = cooling water mass flow rate, kg/s
q1 = mass flow rate of injected tracer, kg/s
C1 = concentration of injected tracer, kg/kg
C2 = concentration of tracer at downstream position during the ‘plateau’ period
of constant concentration, kg/kg
The tracer normally used is sodium chloride.
8. 2-Ultrasonic Flow meters:2-Ultrasonic Flow meters:
Operating on Doppler effect principle, these meters are
non-invasive, meaning measurements can be taken
without disturbing the system. Scales and rust in the
pipes are likely to impact the accuracy
•Ensure measurements are taken in a sufficiently long length of
pipe free from flow disturbance due to bends, tees and other
fittings.
•The pipe section where measurement is to be taken should be
hammered gently to enable scale and rust to fall out.
•For better accuracy, a section of the pipe can be replaced with
new pipe for flow measurements.
9. 3-Tank filling method:3-Tank filling method:
In open flow systems such as water getting pumped to an
overhead tank or a sump, the flow can be measured by
noting the difference in tank levels for a specified period
during which the outlet flow from the tank is stopped.
The internal tank dimensions should be preferable taken
from the design drawings, in the absence of which direct
measurements may be resorted to.
10. 4-Installation of an on-line flow meter:4-Installation of an on-line flow meter:
If the application to be measured is going to be critical
and periodic then the best option would be to install an
on-line flow meter which can get rid of the major
problems encountered with other types.
11. Determination of total head, H:Determination of total head, H:
Suction head (hs)
This is taken from the pump inlet pressure gauge readings and the value to be
converted in to meters (1kg/cm2
= 10. m). If not the level difference between sump water
level to the centerline of the pump is to be measured. This gives the suction head in
meters.
Discharge head (hd)
This is taken from the pump discharge side pressure gauge. Installation of the pressure gauge
in the discharge side is a must, if not already available.
13. S.
No
.
Item Reference Units
Rated Unit-1 Unit-2 Unit-3
1. Unit load MW 200 197 211 196
2. Frequency Hz 50 49.5 49.74 49.53
3. CEP flow M3
/hr 610 510 5.17 525
4. Suction pressure MWC - 3.1 3.3 3.8
5. Discharge pressure MWC - 215.3 215.3 210.3
6. Total head
developed
MWC 190 211.7 211.7 206.5
7. Density @ 400
C Kg/m3
0.9922 0.9922 0.9922 0.9922
8. Liquid power of
pump
kW 313.36 247.67 295.92 293.11
9. Power input to
motor
kW 433.66 414.04 444.15 450.50
10. Motor efficiency % 92.7 92.7 92.7 92.7
11. System efficiency
(pump & motor)
% 72.3 66.36 66.6 65.1
12. CEP efficiency
(pump)
% 78 71.56 71.80 70.19
ILLUSTRATIVE EXAMPLE:CEP Performance & ValveILLUSTRATIVE EXAMPLE:CEP Performance & Valve
LossLoss
14. • The generic opportunities for pumping system energy efficiencyThe generic opportunities for pumping system energy efficiency
improvement include:-improvement include:-
– Operation of the pump at a duty point close to the bestOperation of the pump at a duty point close to the best
efficiency point in terms of head and flow. In other words,efficiency point in terms of head and flow. In other words,
choice of right pump for given duty.choice of right pump for given duty.
– Minimum restrictions in suction path and providing maximumMinimum restrictions in suction path and providing maximum
possible suction head for pump.possible suction head for pump.
– Minimum restrictions in discharge path, especially throttlingMinimum restrictions in discharge path, especially throttling
controls.controls.
– Good maintenance practices to avoid recirculation effects andGood maintenance practices to avoid recirculation effects and
proper condition of impellers (wear-out, pitting, etc).proper condition of impellers (wear-out, pitting, etc).
– Ensuring good dynamic balancing of shaft and fit condition ofEnsuring good dynamic balancing of shaft and fit condition of
bearingsbearings
– Ensuring correct voltage supply.Ensuring correct voltage supply.
– Operating at minimum possible discharge pressure, with respectOperating at minimum possible discharge pressure, with respect
to end use requirements.to end use requirements.
– Rationalizing the pipe size for optimum pressure dropsRationalizing the pipe size for optimum pressure drops
– Minimizing losses in bends/valvesMinimizing losses in bends/valves
– Good housekeeping practicesGood housekeeping practices
– Replacement option by high efficiency pumpsReplacement option by high efficiency pumps
– Need based option of variable speed drives for efficientNeed based option of variable speed drives for efficient
capacity controlcapacity control
15. Fans –Fans –
Purpose of the As run performancePurpose of the As run performance
TestsTests ::
The purpose of such tests is to determine, under actual
operating conditions, the volume flow rate, the power
input and the total pressure rise across the fan.
These test results will provide actual value for the flow
resistance of the air duct system, which can be compared
with the value specified by supplier.
16. Performance Terms andPerformance Terms and
DefinitionsDefinitions
Fan Efficiency: The air power static divided by impeller power
Static Pressure: The absolute pressure at a point minus the reference
atmospheric pressure.
Dynamic Pressure: The rise in static pressure which occurs when air moving with specified
velocity at a point is bought to rest without loss of mechanical energy. It is also known as
velocity pressure.
Total Pressure: The sum of static pressures and dynamic pressures at a point.
Fan Shaft Power: The mechanical power supplied to the fan shaft
Motor Input Power: The electrical power supplied to the terminals of an electric motor drive
(kW)inshafttheinput toPowerx102
mmwcinpressurestaticxSec/minVolume
%EfficiencyFanStatic
3
=
17. ILLUSTRATIVE EXAMPLE :As run Performance of IDILLUSTRATIVE EXAMPLE :As run Performance of ID
FANSFANS
= TPH 1664.9 1130.65 1604.40 1604.40 1769.34
= m3
/sec 572.28 376.19 533.23 541.85 593.38
2 Average Suction Pressure = mmWC NA NA -279.0 -263.6 -237.3
3 Average Discharge Pressure = mmWC NA NA 25.0 25.0 25.0
4 = mmWC 351.8 212.5 304.0 288.6 262.3
Nm/kg 4270.7 2497.4 3568.2 3442.5 3107.0
5 Flue Gas Temp at ID inlet = o
C 144 135 135.3 141.9 139.0
6 Flue Gas Density = kg/m3 0.8081 0.835 0.836 0.822 0.828
7 ID Fan Hyd. Scoop Positrion = % NA NA 94.29 93.78 97.97
8 ID Fan IGV Positrion = % NA NA 81.78 82.43 77.13
9 ID Fan Speed = RPM 689 487 710.65 740.80 746.62
10
ID Fan Motor Input Power
(Electrical) = kW 3960.0 1487.7 2600.0 2566.0 2588.8
11
IDF Motor Output power
( @ 95% motor Effy.) kW 3762.0 1413.3 2470 2437.7 2459.36
12
ID Fan Shaft Power
(@ 75% of Hydr. Coupling Effy.)
kW 2821.5 1060.0 1852.5 1828.3 1844.5
13 ID fan Air Power = kW 1975.03 784.37 1590.22 1534.20 1527.05
14
Combined Efficiency of ID
Fans = % 49.88 52.73 61.16 59.79 58.99
15 Operating Fan Efficiency = % 70.0 74.0 85.84 83.92 82.79
16 SEC KWH/T NA 1.32 1.62 1.60 1.46
17
% Loading on Capacity
(Volumetric Flow) = % Ref 65.7 93.2 94.7 103.7
18 % Loading on Head = % Ref 60.4 86.3 82.0 74.5
19 % Loading On kW = % Ref 41.3 72.3 71.3 72.0
Total Diff. Pressure
Flue Gas Flow At ID Fan Inlet1
1769.34
581.09
-249.3
25.0
274.3
3181.9
130.5
0.846
94.80
74.38
732.65
2615.7
2484.92
1863.7
1563.83
59.79
83.91
1.48
101.5
77.9
72.7
Units Unit 1 Unit 2
Specified 100 % TCMR IDF-1A IDF-1C IDF-2B
Fan Design Unit 2
IDF-2B IDF-2C
18. • The generic opportunities for energy efficiencyThe generic opportunities for energy efficiency
improvements in fans and fan systems include:-improvements in fans and fan systems include:-
– Operation of fan at close to best efficiency duty point.Operation of fan at close to best efficiency duty point.
– Minimum restrictions in suction path (no dampers)Minimum restrictions in suction path (no dampers)
– Minimum restrictions in discharge path (no dampers)Minimum restrictions in discharge path (no dampers)
– Operation at rational head and flow, vis-à-vis processOperation at rational head and flow, vis-à-vis process
requirements.requirements.
– Ensuring correct voltage and frequency at supplyEnsuring correct voltage and frequency at supply
– Good maintenance practicesGood maintenance practices
– Good housekeeping practicesGood housekeeping practices
– Minimizing in leak air / gasMinimizing in leak air / gas
– Minimizing out leak air / gasMinimizing out leak air / gas
– Rationalizing duct size for minimizing pressure dropsRationalizing duct size for minimizing pressure drops
– Minimizing sharp bendsMinimizing sharp bends
– Replacement options by higher efficiency fansReplacement options by higher efficiency fans
– Need based option of variable speed drives if capacityNeed based option of variable speed drives if capacity
control is required for end usecontrol is required for end use
– Minimizing slippage losses in beltsMinimizing slippage losses in belts